- Food-borne infection during pregnancy
- Avoiding food-borne infections during pregnancy
- Toxicity during pregnancy
Eating a balanced and nutritious diet is an important aspect of remaining healthy during pregnancy. Women need to make numerous changes to their diet whilst pregnant, including eating greater quantities of food and specific micronutrients, and also avoiding particular foods which carry health risks for pregnant women.
There are many foods which pregnant women should avoid to reduce their risk of infectious food-borne disease, as many food borne infections are associated with poor pregnancy (e.g. miscarriage) and foetal (e.g. low birth weight) outcomes. In addition, the immune system is weakened during pregnancy due to hormonal changes in the body, so pregnant women have a higher risk of becoming ill from food borne infections. Some foods may also be toxic to a pregnant woman or her foetus if consumed in large amounts during pregnancy, and pregnant women should limit their consumption of these foods.
There are several food-borne infections which occur more commonly in pregnant women and present more serious health risks during pregnancy.
Listeria monocytogenes infection (listeriosis)
Whilst pregnant, women are at an increased risk of infection with the food-borne bacteria Listeria monocytogenes, found in raw meat and soft cheeses. This infection causes upper respiratory tract symptoms, septicaemia (blood infection) and encephalitis (inflammation in the brain) in infected individuals. Although it is relatively uncommon, infection of pregnant women with L. monocytogenes is of particular concern as it can cause miscarriage, stillbirth and premature birth and septicaemia (whole body infection) and pneumonia in newborn babies. Up to 50% of newborns with listeriosis who do not receive treatment die. The infection can also adversely affect a pregnant woman’s health and may sometimes be fatal for pregnant women.
Toxoplasma gondii infection (toxoplasmosis)
Toxoplasma gondii is a protozoan (single-celled organism) found in raw meat and cat faeces. It causes the infectious disease toxoplasmosis and can also be transmitted from a pregnant woman to her foetus. While the infection is not a serious threat to maternal health, it is associated a range of poor health outcomes for the offspring of infected women. These include:
- Chorioretinitis (eye inflammation involving the choroid and retina);
- Mental retardation;
- Hearing loss;
More information on toxoplasmosis.
Salmonellosis is an infectious disease caused by the bacteria Salmonella. It is found in raw animal products (including eggs) and some plant foods (in particular sprouts). It causes nausea, vomiting, abdominal cramps, diarrhoea, fever and headache. While pregnant women are no more likely than those in the general population to experience salmonella infection, it has been linked to miscarriage, and therefore the consequences of infection are more serious for pregnant women.
More information on salmonellosis.
Due to their increased risk of infection with several rare diseases (e.g. listeriosis) and the severe maternal and foetal health consequences of these diseases, pregnant women should avoid foods which are known to harbour disease-causing infectious agents. They should also prepare and store food hygienically, to reduce the risk of these infections.
Maintaining good personal hygiene during pregnancy can reduce the risk of food borne illness and particularly illness associated with Toxoplasmosis from infection with the bacteria T. gondii. This infection often occurs as a result of contamination from unwashed hands which have been in contact with animal faeces, rather than from contaminated food. Hygiene measures which pregnant women should take to avoid the risk of toxoplasmosis and other infectious diseases include:
- Wash hands thoroughly before preparing or eating food and after gardening or touching pets;
- Avoid cat litter including changing the kitty litter tray; and
- Wear gloves when gardening.
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Pregnant women and women who are attempting to conceive should also take additional hygiene precautions when preparing food to reduce the risk of infection. These include:
- Ensure benches, utensils and other food preparation equipment is clean, particularly if it has previously been in contact with raw meat or vegetables;
- Avoid raw meat contaminating other foods by using separate utensils (especially knives and cutting boards) for raw meat and other foods and keeping them in a separate section of the refrigerator;
- Always eat well-cooked meat. Meat is thoroughly cooked when no pink sections are visible (even in the centre of the meat portion) and juices which run out are clear;
- Thaw frozen food in the refrigerator or microwave. Food should not be left on a bench or in the sink to defrost;
- Reheat food to steaming hot (>60°C) and ensure leftover food is kept cold (<5°C) until it is ready to be reheated and eaten; and
- Wash raw foods before eating and wash hands after handling raw foods.
In addition pregnant women can reduce their chance of food borne illnesses during pregnancy by avoiding some types of food. In general it is recommended that pregnant women only eat freshly prepared foods. Leftovers from home-cooked meals can be eaten within 24 hours if they are properly refrigerated at <5°C. However, takeaway foods which may spend considerable periods of time in warming ovens or displays should be avoided.
Pregnant women should also avoid the following foods:
- Raw meat, including raw seafood and raw eggs;
- Unpasteurised milk and other dairy products;
- Soft serve ice cream;
- Soft cheese and pates;
- Chilled ready-to-eat foods including;
- Cold cooked chicken;
- Processed meats;
- Prepared salads;
- Ready-cooked take-away foods;
- Leftovers which are more than 24 hours old or which have not been refrigerated <5°C; and
- All types of sprouts including alfalfa, broccoli, onion, sunflower, clover, radish and snow pea sprouts and mung and soy beans.
|For more information on food hygiene, see Food Poisoning Prevention and Food Safety.|
Some foods may also be toxic (poisonous) if consumed in large quantities by pregnant women.
Excessive mercury consumption during pregnancy may cause toxicity which can harm the developing foetus. Mercury occurs naturally in the environment but is also a component of industrial pollution. It can accumulate in water bodies and the fish and other species which inhabit these bodies of water can accumulate mercury in their flesh and skin. Mercury also builds up in humans (e.g. when it enters the body through consumption of mercury containing fish).
Consumption of excessive amounts of mercury does not affect the health of adult humans but during pregnancy it can adversely affect the foetus. Risk varies depending on the levels of mercury consumed. Consuming low levels of mercury, in line with recommendations made by Australian health authorities (see below) does not present a risk for a pregnant woman or her foetus. Consuming higher levels of mercury (above the levels recommended below) is associated with damage to the nervous system of the foetus.
To avoid mercury toxicity, pregnant women should limit their consumption of fish, as all types of fish contain traces of mercury. Specific types of fish which usually contain high levels of mercury should be avoided or eaten only in small quantities. While Australian fish have relatively low levels of mercury, it is still recommended that women restrict their intake whilst pregnant. The NSW Food Authority recommends that women eat no more than:
- 2-3 serves of fish per week where one serve is 150grams of fish;
- 1 serve of shark (flake) or billfish (Broadbill, Swordfish or Marlin) per fortnight. Women who consume shark or billfish should not consume any other servings of fish in the fortnight;
- 1 serve of orange roughy (sea perch) or catfish per week. Women who consume a serving of orange roughy or catfish should not consume any other servings of fish in the week.
Pregnant women should note that processed fish products such as seafood sticks are typically produced from fish which contain low levels of mercury. It is therefore safe for women to consume 2-3 serves of these products each week.
As mercury builds up in the body over time and levels of mercury in the human body begin to reduce only several months after consumption, women who are planning a pregnancy should also limit their fish consumption to the above recommendations for several months prior to conception.
High levels of caffeine intake (>300mg/day) during pregnancy are potentially harmful. Evidence suggests that consuming >300mg of caffeine per day during pregnancy increases the risk of intrauterine growth retardation (restricted growth in the womb) and spontaneous abortion. It is not yet known whether consuming smaller quantities of caffeine presents health risks during pregnancy.
It is recommended that pregnant women limit their daily intake of caffeine to 200mg per day which is equivalent to:
- 1 mug of ground coffee;
- 2 mugs of instant coffee;
- 2 mugs of tea;
- 5 cans of cola drink;
- 2 cans of energy drink;
- 4 (50g) bars of plain chocolate; or
- 8 (50g) bars of milk chocolate (which contains only half the caffeine of plain chocolate).
For more information, see Caffeine Consumption During Pregnancy.
There is strong evidence that high levels of alcohol consumption during pregnancy cause foetal damage and intrauterine growth retardation.
The Australian National Health and Medical Research Council take a cautious approach and recommends that pregnant women abstain from alcohol consumption completely during pregnancy. Women who do choose to drink alcohol are advised to avoid drinking to the point of intoxication.
More information on alcohol consumption during pregnancy.
For more information about pregnancy, including preconception advice, stages of pregnancy, investigations, complications, living with pregnancy and birth, see Pregnancy.
For more information on nutrition, including information on types and composition of food, nutrition and people, conditions related to nutrition, and diets and recipes, as well as some useful videos and tools, see Nutrition.
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